Risk factors for the presence of antibodies to Toxoplasma gondii in Norwegian slaughter lambs

Abstract

In a study of lambs from 194 sheep flocks from different areas of Norway, 44.3% of the flocks were found seropositive against Toxoplasma gondii using an ELISA test, with antibodies found in 16.2% of the 1940 individual animals. The risk factors for the occurrence of antibodies to Toxoplasma gondii found in the multivariate logistic regression were: daily presence of a young cat in the sheep house (Odds ratio, OR=4.11, 95% CI=1.01–19.7); `atypical' grazing of lambs (OR=6.35, CI=2.36–17.11); use of mouse poison in the sheep house (OR=2.26, CI=1.02–5.00); farm situated at an altitude >100 meters above seal level (101–250 m: OR=1.20, CI=0.49–2.92; 251–500 m: OR=4.97; CI=2.04–12.0; >500 m: OR=3.66, CI=1.33–10.1). A lower risk was found for flocks with perforated metal floors in the sheep house (OR=0.47, CI=0.23–0.96) and timber construction of the sheep house (OR=0.34, CI=0.15–0.80). Based on these findings it was recommended that farmers avoid keeping young cats in the sheep houses, that close-to-farm grazing be kept to a minimum and that perforated metal floors be used in the sheep houses. However, with such a high seroprevalence, the proposed measures alone would not reduce the occurrence of Toxoplasma in lambs to a level where undercooked lamb can be consumed without posing an unacceptable risk for some consumer groups.